Eukaryotes ancient families

Although the building blocks of the eukaryotic cytoskeleton appear to be ancient, the protein domains interacting with it appear to have emerged more recendy. Several actin-binding domain families, namely calponin homology, CH, actin depolymerisation factor (ADF), the Sla2p... 

Secondary transporters are ancient molecular machines, common today in bacteria and archaea as well as in eukaryotes. For example, approximately 160 (of approximately 4000) proteins encoded by the E. coli genome appear to be secondary transporters. Sequence comparison and hydropathy analysis suggest that members of the largest family have 12 transmemhrane helices that appear to have arisen by duplication and fusion of a membrane protein with 6 transmemhrane helices. Included in this family is the lactose permease of E. coli. This symporter uses the H+ gradient... 

Many features of signal-transduction pathways are ancient. For example, cAMP signals the need for energy in prokaryotes as well as eukaryotes, although the mechanisms for detecting cAMP are different. Similarly, the GTP-binding proteins—the subunits of the hetero-trimeric G proteins and the members of the Ras family—are part of an... 

The WD-repeat-containing proteins form a very large family that is diverse in both its function and domain structure. Within all these proteins the WD-repeat domains are thought to have two common features the domain folds into a beta propeller and the domains form a platform without any catalytic activity on which multiple protein complexes assemble reversibly. The fact that these proteins play such key roles in the formation of protein-protein complexes in nearly all the major pathways and organelles unique to eukaryotic cells has two important implications. It supports both their ancient and proto eukaryotic origins and supports a likely association with many genetic diseases. 

Yang et al (2005) have proposed an alternate pathway of manganese induced neurotoxicity that involved eukaryotic ACDP (ancient conserved domain protein) family protein in metal homoeostasis. These authors employed the baker s yeast Saccharomyces cerevisiae as a model system to identify genes that contributed to manganese-related damage. 

Elias M, Archibald JM. The RJL family of small GTPases is an ancient eukaryotic intervention probably functionally associated with flagellar apparatus. Gene. 2009 442 63-72. 

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